1. Field of the Invention
The present invention relates to a coding method for a mobile communication system, and more particularly to a method for effectively performing a channel-coding process on information with various lengths using a block code.
2. Discussion of the Related Art
For the convenience of description and better understanding of the present invention, some concepts requisite for the present invention from among several basic coding theories will hereinafter be described in detail.
Generally, a general binary error correction code is denoted by [n, k, d], where “n” is the number of bits of coded codewords, “k” is the number of information bits created prior to the coding process, and “d” is a minimum distance between codewords. In this case, only the binary code has been considered for the above-mentioned binary error correction code, such that a number of possible codeword points in code space is denoted by 2n, and a total number of coded codewords is denoted by 2k. Also, if the minimum distance is not substantially considered to be important, the aforementioned binary error correction code may also be denoted by [n, k]. If there is no mention of the above error correction code in this application, it should be noted that individual values of “n”, “k”, and “d” be set to the above-mentioned values.
In this case, the above-mentioned error correction code should not be confused with a matrix-type block code composed of X number of rows (i.e., X rows) and Y number of columns (i.e., Y columns).
In the meantime, the coding rate R is defined as a specific value acquired when the number of information bits is divided by the number of bits of each codeword. In other words, the coding rate R is denoted by “k/n”, i.e., R=k/n.
Next, the Hamming distance will hereinafter be described in detail.
If two binary codes having the same number of bits include some bits having different bit values, the above-mentioned Hamming distance is indicative of the number of the above bits having the different bit values. Generally, if the Hamming distance “d” is denoted by d=2a+1, “a” number of errors can be corrected. For example, if one of two codewords is 101011 and the other one is 110010, the Hamming distance between the two codewords is 3.
In the meantime, the term “minimum distance” for use in the coding theory is indicative of a minimum value between two arbitrary codewords contained in a code. The minimum distance is considered to be one of criteria to evaluate the performance of a code. The longer the distance between the codewords generated by the coding process, the lower the probability of mis-detecting a corresponding codeword to be another codeword; as a result, the coding performance becomes better. Performance of a total code is estimated by a minimum distance between codewords having the worst performance. In conclusion, if a minimum distance of a specific code is maximized, this specific code may have a superior performance.
In the next-generation mobile communication system, control information carries system constituent information and transmission channel information, such that it is considered to be very important information to determine a system performance. Generally, this control information has a short length to use a relatively small amount of system resources. The above-mentioned control information is coded by the coding technique very resistant to a channel error, and is then transmitted. A variety of coding schemes for the above control information have been considered in the 3GPP mobile communication system, for example, a short-length block code based on a Reed-Muller (RM) code, a tail-biting convolution code, and a repetition code of a complex code.
In the meantime, the control information for use in the 3GPP LTE system acting as an improved format of the above-mentioned mobile communication system is coded by means of block codes, such that the block-coded control information is then transmitted. In more detail, if the length of a transmission (Tx) information bit is “A”, the channel-coding process is performed by a block code composed of 20 rows and A columns (i.e., (20,A) block code) during the transmission of a specific channel (e.g., Physical Uplink Control Channel (PUCCH)), and the channel-coding result is then transmitted. In the 3GPP LTE system, uplink control information is transmitted over the PUCCH and a PUSCH (i.e., a physical uplink shared channel). The control information transmitted over the PUSCH is channel-coded by a block code composed of 32 rows and A columns (i.e., (32,A) block code), such that the channel-coded control information is then transmitted.
In the meantime, the (32,A) block code may have various formats. It is difficult for the user to search for an optimum format after checking individual coding performances of each length of information bits associated with all block codes.